1. Field of the Invention
The present invention relates to a flux cored wire for arc welding of austenitic stainless steel, and in particular to an improved flux cored wire for arc welding of austenitic stainless steel which can stably perform the welding, by reducing an amount of spatters generated in the arc welding of austenitic stainless steel, especially by preventing a weld metal from being drooped in the vertical-up position welding, and which can also form a stable weld metal at a high temperature.
2. Description of the Related Art
Stainless steel is a kind of alloy steel of steel and Cr having improved corrosion resistance. According to the composition, the stainless steel is classified into Cr group and Crxe2x80x94Ni group. According to the metal structure the stainless steel is classified into martensite group, ferrite group, austenite group, austenite-ferrite group and precipitation hardening group.
The austenitic stainless steel(hereinafter, referred to as xe2x80x98stainless steelxe2x80x99) belongs to the Crxe2x80x94Ni group. The representative stainless steel is 18-8 stainless steel of 18 wt % Cr-8 wt % Ni which has the most economical composition. A variety of steels have been developed therefrom.
Although widely employed due to its superior corrosion resistance, the stainless steel has low weldability. Thus, a welding wire has been improved suitable for the arc welding of the stainless steel, thereby removing defects in a weld metal. However, an amount of spatters generated is increased in the welding, to cause the following problems:
That is, a weld metal is spattered and adhered to a non-weld metal. Accordingly when the welding is finished, an unnecessary process such as grinding is required to remove the metal in the non-weld metal thereby reducing efficiency. In addition a bead is easily drooped in the vertical-up position welding. As a result, the bead has a poor shape, and a succeeding welding is difficult to carry out.
In order to solve the aforementioned problems. Bi containing material is added to a flux composing the welding wire, which increases cracking sensitivity of the weld metal at a high temperature.
Accordingly, an object of the present invention is to provide a flux cored wire for arc welding of austenitic stainless steel which can prevent a welding material from being spattered and a bead from being drooped, by reducing an amount of spatters generated in the welding, and which also can prevent a crack from occurring at a high temperature.
In order to achieve the above-described object of the present invention, a flux containing an alkali metal compound, metal fluoride, SiO2, TiO2, ZrO2, Bi, Mn and Cr is filled in a sheath consisting of stainless steel in an amount of 15 to 35 wt % by weight of the welding wire.
It has been found that when the flux is used in the amount less than 15 wt %, slag covering a surface of the bead is not sufficiently generated, and when the flux is used in the amount greater than 35 wt %, the welding wire is easily bent due to the weight of the flux when feeding.